The preparation of 2-alkylpyrimidines is taught in U.S. Pat. No. 3,050,523. That process requires the reaction of an alkylene 1-3 diamine with an organic carboxylic acid, ester or amide over supported noble metal catalysts having dehydration and dehydrogenation activity. The desired compounds may be obtained by azeotropic distillation or by treatment with carbon dioxide followed by distillation. The work-up procedures are time consuming and the yields are not as good as could be desired.
Lythgoe et al., J. Chem. Soc. 1951, pp. 2323-2329 teach the dehydrogenation of tetrahydro-2-phenylpyrimidine in a current of carbon dioxide.